Migration and proliferation of vascular smooth muscle (VSM) cells occurs during development, wound healing, angiogenesis, and contributes to the progression of vascular disease. Ca2+ signals are known to regulate cell proliferation and motility, although this knowledge has not been well integrated into molecular models, due in part to lack of insight into Ca2+-dependent effector mechanisms and targets. Ongoing work funded by this grant has focused on the structure and function of one major Ca2+ signal effector, namely multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII). VSM cell migration and proliferation are properties of synthetic phenotype cells that have not acquired, or have lost, differentiated contractile protein markers and function. VSM phenotype modulation between differentiated contractile and proliferative/migratory states are of considerable interest and clinical importance, but are incompletely understood. An emerging concept, consistent with results from the past funding period, is that disease- or injury-induced changes in Ca2+ signaling mechanisms and dynamics contributes to development of the migratory/proliferative VSM phenotype promoting vascular wall remodeling. The overall objective of this renewal is to test the concept that Ca2+ signaling via specific CaMKII isoforms, regulates VSM gene transcription and is a determinant of VSM phenotype. This concept will be tested by pursuing three aims: 1.) We will test the hypothesis that CaMKII regulates the co-repressors HDAC4 and HDAC5 in synthetic phenotype VSM. The transcription activator MEF2 will be tested as a CaMKII/HDAC4,5-dependent target affecting gene transcription. CaMKII isoform specificity in coupling to this regulatory pathway be tested. 2.) The function of CaMKII isozymes as regulators of the transcriptional repressor REST/NRSF expression and activity in VSM will be evaluated and HDAC4/5 will be tested as intermediaries. 3.) The function of CaMKII-dependent regulation of HDAC4/5 and REST in regulating VSM phenotype and vascular remodeling will be evaluated in vivo using the balloon-injured rat carotid artery as a model. By elucidating the functional consequences of CaMKII isoform modulation in response to vascular injury, the results of these studies are expected to provide insights into mechanisms underlying phenotypic modulation of VSM cells and mechanism(s) by which Ca2+ signals and a prominent Ca2+-dependent multifunctional protein kinase modulates VSM cell function and contributes to vascular disease.